如何在 Java 中查找整数的长度？

2025 年 5 月 13 日 | 阅读 6 分钟

在本节中，我们将学习 **查找 Java 中整数长度** 的不同方法。整数的长度表示该整数中存在的数字的总数。

我们可以通过以下方法找到整数的长度：

使用 while 循环
使用 String
使用连续乘法
使用对数
使用递归

让我们一一讨论。

使用 while 循环

我们可以使用 while 循环来查找整数的长度。请观察以下代码。

文件名： IntegerLengthExample.java

public class IntegerLengthExample
{
// method to find the number of digits present in the number n
public int countDig(int n)
{
int count = 0;
while(n != 0)
{
// removing the last digit of the number n
n = n / 10;
// increasing count by 1
count = count + 1;
}
return count;
}
// main method
public static void main(String argvs[])
{
// input array
int arr[] = {78, 9, 2345, 899009, 1, 414, 34, 1000, 2749};
// size of the input arrray
int size = arr.length;
// creating an object of the class IntegerLengthExample
IntegerLengthExample obj = new IntegerLengthExample();
for(int i = 0; i < size; i++)
{
int count = obj.countDig(arr[i]);
System.out.println("The length of the number " + arr[i] + " is " + count);
}
}
}

输出

The length of the number 78 is 2
The length of the number 9 is 1
The length of the number 2345 is 4
The length of the number 899009 is 6
The length of the number 1 is 1
The length of the number 414 is 3
The length of the number 34 is 2
The length of the number 1000 is 4
The length of the number 2749 is 4

使用 String

另一种方法是将数字转换为字符串，然后计算其大小。字符串的大小即为字符串的长度。以下程序对此进行了说明。

文件名： IntegerLengthExample1.java

public class IntegerLengthExample1
{
// method to find the number of digits present in the number n
public int countDig(int n)
{
// converting the number n to a string
String str = Integer.toString(n);
// computing the size of the string
int size = str.length();
return size;
}
// main method
public static void main(String argvs[])
{
// input array
int arr[] = {78, 9, 2345, 899009, 1, 414, 34, 1000, 2749};
// size of the input arrray
int size = arr.length;
// creating an object of the class IntegerLengthExample1
IntegerLengthExample1 obj = new IntegerLengthExample1();
for(int i = 0; i < size; i++)
{
int count = obj.countDig(arr[i]);
System.out.println("The length of the number " + arr[i] + " is " + count);
}
}
}

输出

The length of the number 78 is 2
The length of the number 9 is 1
The length of the number 2345 is 4
The length of the number 899009 is 6
The length of the number 1 is 1
The length of the number 414 is 3
The length of the number 34 is 2
The length of the number 1000 is 4
The length of the number 2749 is 4

使用连续乘法

我们可以将数字 1 乘以 10，直到它大于数字 n。每次乘以 10 时，我们将计数变量加 1。计数器的最终值即为整数 n 的长度。让我们通过以下程序来理解它。

文件名： IntegerLengthExample2.java

public class IntegerLengthExample2
{
// method to find the number of digits present in the number n
public int countDig(int n)
{
int temp = 1;
int count = 0;
while(temp <= n)
{
// multiplying temp by 10
temp = temp * 10;
// increasing the value of count by 1
count = count + 1;
}
// count contains the total number of 
// digits present in the number n
return count;
}
// main method
public static void main(String argvs[])
{
// input array
int arr[] = {78, 9, 2345, 899009, 1, 414, 34, 1000, 2749};
// size of the input arrray
int size = arr.length;
// creating an object of the class IntegerLengthExample2
IntegerLengthExample2 obj = new IntegerLengthExample2();
for(int i = 0; i < size; i++)
{
int count = obj.countDig(arr[i]);
System.out.println("The length of the number " + arr[i] + " is " + count);
}
}
}

输出

The length of the number 78 is 2
The length of the number 9 is 1
The length of the number 2345 is 4
The length of the number 899009 is 6
The length of the number 1 is 1
The length of the number 414 is 3
The length of the number 34 is 2
The length of the number 1000 is 4
The length of the number 2749 is 4

使用对数

我们也可以使用 log 来查找整数的长度。请观察以下程序。

文件名： IntegerLengthExample3.java

public class IntegerLengthExample3
{
// method to find the number of digits present in the number n
public int countDig(int n)
{
// finding the length of the number n using the log10() method
int len = (int) (Math.log10(n) + 1);
// returning the  length
return len;
}
// main method
public static void main(String argvs[])
{
// input array
int arr[] = {78, 9, 2345, 899009, 1, 414, 34, 1000, 2749};
// size of the input arrray
int size = arr.length;
// creating an object of the class IntegerLengthExample3
IntegerLengthExample3 obj = new IntegerLengthExample3();
for(int i = 0; i < size; i++)
{
int count = obj.countDig(arr[i]);
System.out.println("The length of the number " + arr[i] + " is " + count);
}
}
}

输出

The length of the number 78 is 2
The length of the number 9 is 1
The length of the number 2345 is 4
The length of the number 899009 is 6
The length of the number 1 is 1
The length of the number 414 is 3
The length of the number 34 is 2
The length of the number 1000 is 4
The length of the number 2749 is 4

使用递归

我们也可以使用递归来找出整数的长度。以下程序对此进行了演示。

文件名： IntegerLengthExample4.java

public class IntegerLengthExample4
{
// method to find the number of digits present in the number n
public int countDig(int n)
{
// handling base case
if(n / 10 == 0)
{
return 1;
}
// recrusively finding the length of the integer n
return 1 + countDig(n / 10);
}
// main method
public static void main(String argvs[])
{
// input array
int arr[] = {78, 9, 2345, 899009, 1, 414, 34, 1000, 2749};
// size of the input array
int size = arr.length;
// creating an object of the class IntegerLengthExample4
IntegerLengthExample4 obj = new IntegerLengthExample4();
for(int i = 0; i < size; i++)
{
int count = obj.countDig(arr[i]);
System.out.println("The length of the number " + arr[i] + " is " + count);
}
}
}

输出

The length of the number 78 is 2
The length of the number 9 is 1
The length of the number 2345 is 4
The length of the number 899009 is 6
The length of the number 1 is 1
The length of the number 414 is 3
The length of the number 34 is 2
The length of the number 1000 is 4
The length of the number 2749 is 4

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如何在 Java 中查找整数的长度？

使用 while 循环

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使用递归

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如何在 Java 中查找整数的长度？

使用 while 循环

使用 String

使用连续乘法

使用对数

使用递归

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